The present invention relates to a new and improved test apparatus for the checking of test objects, typically protective relays, especially voltage, current and/or frequency relays for protecting generators of a power supply network.
This test apparatus comprises a first circuit for generating and transforming test signals or magnitudes which are to be delivered to the test object, a second circuit for pre-programming the test signals or magnitudes which are to be delivered to the test objects, a signal and control device for controlling the course of the test, and a measuring device for measuring the relay response values.
Test devices of the previously mentioned type, wherein for testing a relay the test signal or magnitude is supplied to the primary side of the relay and the test is designated as a so-called "primary checking" or "primary test", have been known for quite some time. However, these devices possess the drawbacks that complicated equipment is needed for producing the test signals or magnitudes, which may be for instance variable voltages, currents or frequencies, to be delivered to the test objects. With numerous protective devices taught to the art by the assignee of this application, potentiometers having movable parts are employed for producing variable test voltages. These potentiometers are prone to disturbance during operation and are complicated to control. In order to test frequency relays there are provided complicated means for measuring the relay frequency. Further, the heretofore known test devices are collectively complicated and expensive.